Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal (L) and his uncle and coach Toni Nadal take part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal gestures during a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal (R) and his uncle and coach Toni Nadal take part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal (R) and his his uncle and coach Toni Nadal take part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

Spanish tennis player Rafael Nadal takes part in a training session in Manacor on the Spanish Balearic Island of Mallorca on January 30, 2013. Nadal, who has been sidelined since June by a left knee injury and then a stomach complaint, will take part in the Vina del Mar tournament in Chile. AFP PHOTO/ Jaime REINA (Photo credit should read JAIME REINA/AFP/Getty Images)

SITGES, SPAIN - NOVEMBER 26: Rafael Nadal attends a press conference for 'Champions Drink Responsibly' by Bacardi on November 26, 2012 in Sitges, Spain. (Photo by Robert Marquardt/Getty Images)

SITGES, SPAIN - NOVEMBER 26: Rafael Nadal attends a press conference for 'Champions Drink Responsibly' by Bacardi on November 26, 2012 in Sitges, Spain. (Photo by Robert Marquardt/Getty Images)

Spain's Rafael Nadal (L) congratulates Spain's Juan Carlos Ferrero during a ceremony in his honour at the Open 500 Valencia at the Agora space in Valencia, on October 24, 2012. Former world number one Juan Carlos Ferrero had announced in mid-September during the Davis Cup semi-final with the United States his retirement from professional tennis in October after a 14-year career in which he won 16 tour titles. AFP PHOTO / JOSE JORDAN (Photo credit should read JOSE JORDAN/AFP/Getty Images)

FILE - This June 10, 2012 file photo shows Rafael Nadal wiping his face as he plays Serbia's Novak Djokovic during their men's final match in the French Open tennis tournament at Roland Garros stadium in Paris. Nadal still has no timetable for his return from a knee injury. The Spaniard hasn't played since losing in the second round of Wimbledon in June to little-known Lukas Rosol. (AP Photo/David Vincent, File)

Rafael Nadal of Spain Lukas reacts after losing a point to Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain lies on the court after failing to return a shot to Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain lies on the court after failing to return a shot to Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts during a second round men's singles match against Lukas Rosol of the Czech Republic at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain plays a return to Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain plays a return to Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts after winning a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts after winning a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain plays a return to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts during a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain returns a shot to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain plays a return to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts during a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain chases down a shot by Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain returns a shot to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain returns a shot to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain returns a shot to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain returns a shot to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain serves to Thomaz Bellucci of Brazil during a first round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain acknowledges the crowd before a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)

FILE This Thursday May 10, 2012 file photo shows Spain's Rafael Nadal returning the ball to Spain's Fernando Verdasco, during the Madrid Open tennis tournament, in Madrid. The blue clay that made Rafael Nadal and Novak Djokovic feel, well, blue at last month's Madrid Open is going away. In a posting on the tour's Web site Saturday June 23, 2012, ATP President Brad Drewett says he decided blue clay courts will not be allowed at tour events next season. After losses, Nadal and Djokovic said they didn't like the way the courts played and vowed not to return in 2013 unless a change was made. (AP Photo/Daniel Ochoa de Olza, File)

Spain's Rafael Nadal ponders during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

LONDON, ENGLAND - JUNE 28: Rafael Nadal reaches for a shot during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

Spain's Rafael Nadal plays a forehand shot during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal plays a forehand shot during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal changes his shirt between games during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal towels himself down between points during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal prepares to receive during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal takes a tumble during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal plays a shot during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal reacts after taking a point in the fourth set during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

Spain's Rafael Nadal reacts after taking a point in the fourth set during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal reacts after a point in the fourth set during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / LEON NEAL RESTRICTED TO EDITORIAL USE (Photo credit should read LEON NEAL/AFP/GettyImages)

Spain's Rafael Nadal reacts after a point in the fourth set during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / LEON NEAL RESTRICTED TO EDITORIAL USE (Photo credit should read LEON NEAL/AFP/GettyImages)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

Spain's Rafael Nadal gestures during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal plays a forehand shot during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

Spain's Rafael Nadal plays a shot during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

Spain's Rafael Nadal gestures during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

LONDON, ENGLAND - JUNE 28: Rafael Nadal of Spain reacts during his Gentlemen's Singles second round match against Lukas Rosol of the Czech Republic on day four of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 28, 2012 in London, England. (Photo by Clive Rose/Getty Images)

Spain's Rafael Nadal reacts after breaking serve in the fourth set during his second round men's singles match against Czech Republic's Lukas Rosol on day four of the 2012 Wimbledon Championships tennis tournament at the All England Tennis Club in Wimbledon, southwest London, on June 28, 2012. AFP PHOTO / MIGUEL MEDINA RESTRICTED TO EDITORIAL USE (Photo credit should read MIGUEL MEDINA/AFP/GettyImages)

FILE - This Aug. 30, 2011 file photo shows Rafael Nadal, of Spain, serving to Andrey Golubev, of Kazakhstan, during the first round of the U.S. Open tennis tournament in New York. The U.S. Open says that Nadal has withdrawn from the last Grand Slam tennis tournament of the year because of injury. (AP Photo/Charles Krupa, File)

FILE - This Sept. 10, 2011 file photo shows fans watching Rafael Nadal of Spain play Andy Murray of Britain as the sun sets over the New York City skyline during a semifinal match at the U.S. Open tennis tournament in New York. The U.S. Open says that Nadal has withdrawn from the last Grand Slam tennis tournament of the year because of injury. (AP Photo/Charlie Riedel, File)

FILE - This Sept. 12, 2011 file photo shows Rafael Nadal of Spain returning a shot to Novak Djokovic of Serbia during the men's championship match at the U.S. Open tennis tournament in New York. The U.S. Open says that Nadal has withdrawn from the last Grand Slam tennis tournament of the year because of injury. (AP Photo/Charles Krupa, FIle)

FILE - In this Aug. 17, 2008, file photo, Rafael Nadal of Spain, reacts following his defeat of Fernando Gonzalez of Chile, in the men's singles gold medal tennis match at the Beijing 2008 Olympics in Beijing. Nadal said Thursday, July 19, 2012, that he won't compete in the tennis event of the London 2012 Olympics. (AP Photo/Elise Amendola, File)

FILE - In this March 20, 2010 file photo, Rafael Nadal of Spain returns a shot to Ivan Ljubicic of Croatia during their match at the BNP Paribas Open tennis tournament in Indian Wells, Calif. Rafael Nadal has pulled out of the London Olympics, saying he is 'not in condition' to compete. Nadal said in a statement Thursday July 19, 2012 it is one of the saddest moments of his career and that he will not travel with the Spanish delegation to London. He was set to be the flag bearer for Spain during the opening ceremony. Nadal won gold in Beijing in 2008. (AP Photo/Mark J. Terrill, File)

Rafael Nadal of Spain waits at the net after being defeated by Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain dries himself off after he lost the third set to Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain runs to try and play a return against Lukas Rosol of the Czech Republic during a second round men's singles match at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts during a second round men's singles match against Lukas Rosol of the Czech Republic at the All England Lawn Tennis Championships at Wimbledon, England, Thursday, June 28, 2012. (AP Photo/Anja Niedringhaus)

Rafael Nadal of Spain reacts after winning a first round men's singles match against Thomaz Bellucci of Brazil at the All England Lawn Tennis Championships at Wimbledon, England, Tuesday, June 26, 2012. (AP Photo/Anja Niedringhaus)